(Last week, we introduced the AMIE project, developed at Oak Ridge National Laboratory (ORNL). It is a system consisting of a house and a car, both three-D printed in carbon fiber composite, that can share electrical energy back and forth between them on a fluid basis, creating a partially independent and energy-resilient living option.)
The process of building it is perhaps the most promising part of the story. The idea of using 3-D printing to build major components was not just to perfect the additive manufacturing process for a house or a car. It allowed the researchers the flexibility to try, fail, change, and try again extremely quickly. As Roderick Jackson puts it, 3-D printing allowed them to “turn the whole innovation cycle on its head.”
It should be pointed out that additive carbon fiber fabrication is a process still in its infancy. Most carbon fiber applications today are constructed from carbon fiber fabric laid up in layers on a mold. Extruded ABS with randomly distributed short carbon fibers is not yet widely used, and AMIE was at the cutting edge.
Rick Spears, whose company Tru-Design brought the 3-D printing know-how to the project, recalls the beginnings of that process. “When we first got involved, they said they were going to print a car, and I said “Yeah right.” But 8 months later, we finished a Shelby Cobra: printed, assembled and finished in 6 weeks during the holiday season.” That included not only printing the car frame and shell, but figuring out the design, and refining the various finishing processes necessary to take a 3-D printed body and make it look like a car you could take to the Detroit Auto Show (which they did).
The potential of this process for the automotive industry is enormous. The old method of designing a car involves making a model in clay, wind tunnel testing it, revising it, and eventually spending a fortune to create the tooling needed to reproduce it in metal. 3-D printing in the design phase of the process significantly speeds things up, eliminating the tedious clay modeling. It shortens the design-test cycle by many months and hundreds of thousands of dollars. “When we took it to the show,” recounts Spears, “someone asked me why would you bring a Shelby Cobra to the Detroit Auto Show. I said this one’s a little different. If you look, it’s been 3-D printed. He said, ‘do you know how long it takes me to get a concept car to the wind tunnel? Eight months, and it’s still clay and it’s not drivable.’ He was the lead design engineer for KIA.”
And of course, going to 3-D printed carbon fiber composite for the final product means tool-less production. By doing away with molds and mold-making, they shortcut the production process significantly. The sacrifice made by using this type of material is the loss of the ability to use the directionality of the fabric to engineer the handling of loads.
The printer they used is, according to ORNL, currently the largest in the world. When they began working with it, it was building at a rate of about 10-12 lbs of composite per hour. It took several days to print a single panel of the house. By the time they finished developing it, it was pumping out 80 lbs per hour, so they could make a panel in about 6 hours. Moreover, this building technology eliminates waste, and lowers energy consumption for construction.
Spears offers another example of how 3-D printing short-cut the design time frame. There is an aluminum frame at the end of the house. When they tried to install it, it proved to be a half-inch too big. The aluminum manufacturer estimated that re-engineering and remaking the frame would take 6-8 weeks. Instead, the ORNL team re-printed part of the frame in carbon fiber, in two hours.
“To me,” say Spears, “that’s the story. It’s cool this is the biggest printer in the world right now, but to be able to solve something like that so fast, that’s amazing.”
You may be thinking that carbon fiber is an impractically expensive material for building houses, and Roderick Jackson would not disagree with you. Carbon fiber and 3-D printing were always understood as a means to an end. It gave them a way to develop the concepts and keep prototyping quickly. The entire project took only 9 months.
“The material we chose was never meant to be the material people would use in the future. The material we chose is the beginning of the steps down that path to being able to use locally available materials. That was the material of choice to achieve the structural performance that we wanted for this project. There were other solutions we could have evaluated in this world of rapid innovation. We chose something that would work, and that would demonstrate, and from which we could learn.”